build: add support for conan and make vendored json optional

CMakeLists.txt

@@ -2,7 +2,11 @@ cmake_minimum_required(VERSION 3.5.0)
 project(cpp-jwt)
 
 option(CPP_JWT_BUILD_EXAMPLES "build examples" ON)
-option(CPP_JWT_BUILD_TESTS "build examples" ON)
+option(CPP_JWT_BUILD_TESTS "build tests" ON)
+option(CPP_JWT_USE_VENDORED_NLOHMANN_JSON "use vendored json header" ON)
+
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_BINARY_DIR})
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_BINARY_DIR})
 
 # only set compiler flags if we are the main project, otherwise let the main
 # project decide on the flags
@@ -14,6 +18,10 @@ endif()
 
 find_package(OpenSSL REQUIRED)
 
+if(NOT CPP_JWT_USE_VENDORED_NLOHMANN_JSON)
+  find_package(nlohmann_json  REQUIRED)
+endif()
+
 # ##############################################################################
 # LIBRARY
 # ##############################################################################
@@ -24,6 +32,10 @@ target_include_directories(
   INTERFACE $<BUILD_INTERFACE:${${PROJECT_NAME}_SOURCE_DIR}/include>
             $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 target_link_libraries(${PROJECT_NAME} INTERFACE OpenSSL::SSL)
+if(NOT CPP_JWT_USE_VENDORED_NLOHMANN_JSON)
+  target_link_libraries(${PROJECT_NAME} INTERFACE nlohmann_json::nlohmann_json)
+  add_definitions(-DCPP_JWT_USE_VENDORED_NLOHMANN_JSON)
+endif()
 target_compile_features(${PROJECT_NAME} INTERFACE cxx_std_14)
 
 # ##############################################################################

README.md

@@ -209,12 +209,27 @@ Tested with <strong>clang-5.0</strong> and <strong>g++-6.4</strong>.
 With issue#12, <strong>VS2017</strong> is also supported.
 
 ## Installation
-Use the C++ package manager..... just kidding :)
-This is a header only library, so you can just add it to your include path and start using it. The only somewhat tricky part is to link it with openssl library. Check out the cmake file for building it properly.
 
-For example one can run cmake like:
+### using conan
+
+```shell
+mkdir build
+cd build
+conan install .. --build missing
+cmake ..
+cmake --build . -j
 ```
-cmake -DOPENSSL_ROOT_DIR=/usr/local/Cellar/openssl/1.0.2j -DGTEST_ROOT=$HOME/googletest
+
+### using debian
+
+```shell
+sudo apt install nlohmann-json3-dev 
+sudo apt install libgtest-dev
+sudo apt install libssl-dev
+mkdir build
+cd build
+cmake ..
+cmake --build . -j
 ```
 
 ## Parameters

conanfile.txt

@@ -0,0 +1,10 @@
+[requires]
+gtest/1.10.0
+nlohmann_json/3.7.0
+openssl/1.1.1d
+
+[generators]
+cmake_find_package
+cmake_paths
+
+[options]

include/jwt/json/test_json.cc

@@ -1,7 +1,10 @@
 #include <iostream>
 #include <string>
+#if defined( CPP_JWT_USE_VENDORED_NLOHMANN_JSON)
 #include "./json.hpp"
-
+#else
+#include "nlohmann/json.hpp"
+#endif
 using json = nlohmann::json;
 
 void basic_json_test()

include/jwt/jwt.hpp

@@ -38,8 +38,11 @@ SOFTWARE.
 #include "jwt/string_view.hpp"
 #include "jwt/parameters.hpp"
 #include "jwt/exceptions.hpp"
+#if defined(CPP_JWT_USE_VENDORED_NLOHMANN_JSON)
 #include "jwt/json/json.hpp"
-
+#else
+#include "nlohmann/json.hpp"
+#endif
 // For convenience
 using json_t = nlohmann::json;
 using system_time_t = std::chrono::time_point<std::chrono::system_clock>;